Fluids based on fluorocarbon compounds are widely used in vapor-compression heat-transfer systems, in particular air conditioning, heat pump, refrigeration and freezing devices. These devices have in common the fact that they are based on a thermodynamic cycle comprising the vaporization of the fluid at low pressure (in which the fluid absorbs heat); the compression of the vaporized fluid up to a high pressure; the condensation of the vaporized fluid to liquid at high pressure (in which the fluid releases heat); and the expansion of the fluid in order to complete the cycle.
Vapor compression heat-transfer systems comprise at least two heat exchangers, one in which the fluid vaporizes, and the other in which it condenses. Heat exchangers may be of cocurrent type or of countercurrent type.
The choice of a heat-transfer fluid (which may be a pure compound or a mixture of compounds) is dictated, on the one hand, by the thermodynamic properties of the fluid, and on the other hand, by additional constraints. Thus, one particularly important criterion is that of the impact of the fluid considered on the environment. In particular, chlorinated compounds (chlorofluorocarbons and hydrochlorofluorocarbons) have the disadvantage of damaging the ozone layer. Henceforth, generally non-chlorinated compounds such as hydrofluorocarbons, fluoroethers and fluoroolefins are therefore preferred to them.
Heat-transfer fluids currently used are HFC-134a, R404a (ternary mixture of 52% of HFC-143a, 44% of HFC-125 and 4% HFC-134a), R407c (ternary mixture of 52% of HFC-134a, 25% of HFC-125 and 23% of HFC-32) and R410a (binary mixture of 50% of HFC-32 and 50% of HFC-125).
It is, however, necessary to develop other heat-transfer fluids that have a global warming potential (GWP) lower than that of the fluids above, and that have equivalent or improved performance levels.
Document WO 2007/002625 describes compositions based on fluoroolefins, and in particular on HFO-1234yf or on HFO-1234ze, in various uses, and in particular as heat-transfer fluids. The document does not specify the type of heat exchanger used.
Document WO 2007/126414 describes generally a large variety of fluoroolefin-based compositions and a large variety of uses of these compositions. The document does not specify the type of heat exchanger used.
Documents WO 2009/107364, WO 2009/110228 and WO 2009/116282 describe refrigeration apparatuses in which the refrigerants used are mixtures based on HFO-1234yf and on HFC-32, optionally supplemented or replaced with other compounds, such as HFC-125. The type of heat exchanger used is not specified.
Document US 2009/0158771 describes the use of a ternary mixture comprising HFC-32, HFC-134a and HFO-1243zf, in a heat transfer application. The coefficients of performance that are obtained are lower than those of the fluid taken as reference, namely HFC-134a. The type of heat exchanger used is not specified.
Document WO 2009/150763 describes an air-conditioning apparatus with a countercurrent heat exchanger, in which the heat-transfer fluid is a mixture of an HFO-1234 and of HFC-32 or of HFC-41.
Document WO 2010/000993 describes the use of a ternary mixture comprising HFO-1234yf, HFC-32 and HFC-134a, as a heat-transfer fluid. The document does not specify the type of heat exchanger used.
Document WO 2010/000994 describes the use of a ternary mixture comprising HFO-1234yf, HFC-32 and HFC-152a, as a heat-transfer fluid. The document does not specify the type of heat exchanger used.
However, there is still a need to develop other heat-transfer fluids that have a relatively low GWP and that have good energy performance levels, in particular in applications using countercurrent heat exchangers.